10 



11 



12 



13 



14 

 15 



16 

 17 

 18 

 19 



20 



21 

 22 

 23 

 24 



90 Cumacea: 11. Diastylidae, 1. Diastylis 



Carapace with few ridges 3. D. planifrons 



Carapace with many ridges — 5. 



Carapace 6 — ridged 4. D. alaskensis 



Carapace 10 — ridged 5. D. anderssoni 



Uropods with endopod longer than the exopod — 7. 



Uropods with endopod not longer than the exopod — 9. 



Peduncle of uropods about twice as long as the telson . . 6. D. hanunoniae 



Peduncle of uropods not nearly twice as long as the telson — 8. 



Telson shorter than fifth segment of the pleon 7. D. antillensis 



Telson longer than fifth segment of the pleon 8. D. koreanus 



Pedigerous segments 3, 4, with dorsal separation faint . . 9. D. algoae 

 Pedigerous segments 3, 4, with dorsal separation distinct — 10. 

 Telson longer than peduncle of uropods — 11. 

 Telson not longer than peduncle of uropods — 12. 



Pedigerous segments and pleon sjjinulose 10. D. spinulosus 



Pedigerous segments and pleon smooth 11. D, armatus 



( Post-anal part of telson distinctly the longer — r 13. 



( Post-anal part of telson not distinctly the longer — 25. 



{Pedigerous segment 5 with hind corners acutely pro- 

 duced — 14. 

 Pedigerous segment 5 with hind corners not acutely pro- 

 duced — 19. 

 I Carapace of female with very conspicuous spines — 15. 

 ) Carapace without very conspicuous spines — - 16. 



I Hind margin of carapace conspicuously upturned . . . . 12 D. bispinosus 

 ) Hind margin of carapace not conspicuously upturned . . . 13. D. cornutus 



I Carapace smooth 14. D. laevis 



( Carapace more or less denticulate — 17. 



j No distinct eye 15. D. sulcatus 



\ Eye distinct — 18. 



I Peraeopod 2 with 7th joint longer than 6th 16. D. rathkii 



\ Peraeopod 2 with 7th joint not longer than 6th 17. D. bradyi 



( Eye wanting or inconspicuous — 20. 

 \ Eye distinct — 22. 



Pleon segments 1 — 5 with hind angles acutely produced 



outwards 18. D. goodsiri 



t Pleon segments 1 — 5 with hind angles not produced out- 

 wards — 21. 



( Pleon spinulose 19. D. stygius 



\ Pleon not spinulose 20. D. polaris 



I Carapace without transverse pleats — 23. 

 \ Carapace with transverse pleats — 24. 



I Pleon unarmed 21. D. lucifer 



\ Pleon segments 1 — 3 with strong dorso-lateral teeth . . .22. D. rugosoides 

 ( Carapace with 5 pairs of obliquely transverse pleats ... 23. D. seorpioides 



\ Carapace with fewer than 5 pairs of pleats 24. D. rugosus 



I Eye distinct — 26. 



\ Eye wanting or obscure — 27. 



) Pseudorostral lobes not much produced 25. D. tumidus 



I Pseudorostral lobes well produced 26. D. neapolitanus 



j Pedigerous segment 5 with hind corners acutely produced — 28. 

 27 J Pedigerous segment 5 with hind corners not acutely pro- 

 l duced — 29. 



